A　dahlia-liked　carbon　nanohorns　(CNHs)　decorated　graphene/polyaniline　(CGP)　nanocomposite　was　prepared　via　in　situ　chemical　oxidation　and　hydrazine　hydrate　reducing.　Firstly,　dahlia-liked　CNHs　decorated　graphene　oxide/polyaniline　(CGOP)　composite　was　synthesized　from　the　polymerization　of　aniline　monomers　on　the　surface　of　graphene　oxide　with　spherical　dahlia-liked　carbon　nanohorns　as　spacers.　Then,　the　CGP　composite　was　obtained　by　reducing　CGOP　using　hydrazine　hydrate.　CGP　exhibited　a　uniform　three-dimensional　nanostructure　because　long　cone-shaped　tips　of　dahlia-liked　CNHs　spacers　can　boost　the　isolation　effect　of　the　nanocomposite.　The　maximum　specific　capacitance　of　CGP　was　up　to　769　F　g−1　at　a　current　density　of　1　A　g−1　when　served　as　supercapacitors　electrodes.　Importantly,　CGP　also　performed　a　good　rate　capability　and　high　stability.　Furthermore,　a　CGP-based　asymmetric　supercapacitor　was　assembled　and　delivered　an　energy　density　of　19.1　Wh　kg−1　at　a　power　density　of　1504.9　W　kg−1.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim